1.1 This specification covers chromium-tungsten-molybdenum-vanadium, with or without tantalum, alloy steel plates intended primarily for welded boilers and pressure vessels designed for elevated temperature service.

1.2 Plates are available under this specification in two grades having different alloy contents as follows:

Grade

NominalChromiumContent, %

NominalTungstenContent, %

NominalMolybdenum Content, %

NominalVanadiumContent, %

NominalTantalumContent, %

315

3.00

1.50

0.75

0.25

315T

3.00

1.50

0.75

0.25

0.10

1.3 The maximum thickness of plates is limited only by the capacity of the composition to meet the specified mechanical property requirements.

1.4 The specification is expressed in both inch-pound units and in SI units; however, unless the order specifies the applicable "M" specification designation (SI units), the plates are furnished to inch-pound units.

1.5 The values stated in either inch-pound units or SI units are to be regarded separately as standard. Within the text, the SI units are shown in brackets. The values stated in each system are not exact equivalents; therefore, each system is to be used independently of the other.